The Adams Arms Pistol-Length Tactical Evo AR-15 Complete Upper Assembly has everything you need in a piston upper assembly. This upper receiver can be connected to any standard AR-15 lower receiver.

Piston systems increase overall reliability while also decreasing the amount of maintenance required to keep the firearm operational. The short stroke gas piston operating system is designed to run cooler and cleaner than a standard direct impingement system. The Adams Arms AR-15 piston system parts and the barrel have been treated with a salt nitride meloniting process making them harder and more corrosive resistant than hard chrome.

Because the piston chamber is the same size as the chamber on the rest of the Adams Arms gas lengths, this 7.5" upper now has the proper dwell time to get the cyclic rate and bullet velocity needed to make this a viable short-barreled option for any CQB scenarios. The free floating forearm by Samson Manufacturing is a 12" tube that extends along the sides and bottom of the gas block, giving you enough space to mount the removable Picatinny rail pieces to meet any of your needs.